diff options
| -rw-r--r-- | Modules/itertoolsmodule.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c index e60ad5b..3d39fa2 100644 --- a/Modules/itertoolsmodule.c +++ b/Modules/itertoolsmodule.c @@ -3076,12 +3076,15 @@ static PyTypeObject cwr_type = { /* permutations object ******************************************************** def permutations(iterable, r=None): - 'permutations(range(3), 2) --> (0,1) (0,2) (1,0) (1,2) (2,0) (2,1)' + # permutations('ABCD', 2) --> AB AC AD BA BC BD CA CB CD DA DB DC + # permutations(range(3)) --> 012 021 102 120 201 210 pool = tuple(iterable) n = len(pool) r = n if r is None else r - indices = range(n) - cycles = range(n-r+1, n+1)[::-1] + if r > n: + return + indices = list(range(n)) + cycles = list(range(n, n-r, -1)) yield tuple(pool[i] for i in indices[:r]) while n: for i in reversed(range(r)): |